Dear All
I have a Vacuum Residue feed drum whose design pressure is 25 barg. A PSV is provided for the drum. I have N2 blanketing to that drum to maintain its pressure @ 16 barg. I have a control valve with bypass on the N2 line. N2 used is HP Nitrogen @ 170 barg. The bypass line contains a restriction orifice and a globe valve in the same order . The main control valve doesn't have a RO.
1) I would like to know why both globe valve(control valve ) and RO are needed on bypass line.
2) If it is to reduce the PSV size during the inadvertent bypass opening case, then we should also have an RO on main control valve line as the CV can fail open.
3) I have a split range control between the N2 inlet and a valve on vent line(split range blanketing system). What is the purpose of by pass lines on control valves of a split range blanketing. Does the operator control the blanketting manually in case any one of the main valve fails?
4) I was thinking the bypass valve will be an indentical to main valve except that it is manually operate. Please correct me if i am wrong.
Attaching the diagram for reference.